Conventional radiographic devices are structured such as illustrated in FIG. 6. The radiation that is incident into the radiographic device is converted into an electric charge through an x-ray converting layer 2 that is structured from a semiconductor thick-film such as amorphous selenium. This charge is read out by a bias voltage VA that is applied between a bias applying electrode 1, which is provided on the incident radiation side of the x-ray converting layer 2, and the ground side of a capacitor Ca, described below, through a TFT substrate 3 that is provided on the side that is opposite of the bias applying electrode 1. This TFT substrate 3 has pixel electrodes 31 that are disposed in the form of a matrix in order to collect the electric charge, capacitors Ca that are connected to the pixel electrodes 31, and thin-film transistor elements Tr, with the sources thereof connected to the capacitors Ca. Note that the region wherein a single pixel electrode 31 is able to collect charge shall be termed the applicable pixel DU, below. The TFT substrate 3 has gate lines G wherein the gates of all of the thin-film transistor elements Tr belonging to the same row are connected in common, and data lines G, wherein the drains of all of the thin-film transistor elements Tr that belong to the same column are connected in common, where the number of gate lines G and the number of data lines D are equal to the number of rows and columns, respectively.
The charge that is produced in the pixel DU is stored in the capacitor Ca through the corresponding pixel electrode 31. When the charge that is stored causes the potential of the gateline G of the column to which the pixel DU belongs to reach the ON potential, then the thin-film transistor elements TR is turned ON, and that charge is read out on the dataline of the column to which the pixel DU belongs. The potential of a gateline G for an individual row is controlled by a gate driving circuit 5.
On the other hand, the TFT substrate 3 is held on one of the surfaces of a base substrate 4, made of aluminum, or the like, and amplifier and A/D converter circuits 6 are disposed on the other surface of this base substrate. The data lines D of the TFT substrate 3, and charge amps 61 of the amplifier and A/D converting circuits 6 are connected by a flexible circuit board 63. The charge that is read out to the data line D is converted into a voltage by the charge amp 61, and after conversion into a pixel value by an A/D converter circuit 62 that is connected to the charge amp 61, [the data value] is stored to a memory unit 71.
After this process has been performed for all of the pixels DU that are subject to reading, then the pixel values that have been stored in the memory unit 71 are sent to an image processing device 8. This series of operations is controlled by a controller 7. (See, for example, Japanese Unexamined Patent Application Publication 2006-325631.)
In a radiographic device structured in this way, there is a problem in that changes in temperature can cause damage to the x-ray converting layer 2, and can cause peeling or cracking of the layer due to differences in the coefficients of thermal expansion from that of the active-matrix substrate on which is formed the thin-film transistor elements, which has the x-ray converting layer 2.
Given this, a radiographic device further comprising a thermistor 91 for detecting the temperature of the x-ray converting layer 2, a Peltier element 92 for changing the temperature of the x-ray converting layer 2, and temperature controlling means for controlling a voltage applied to the Peltier element 92 based on the detected temperature, has been proposed. (See, for example, Japanese Unexamined Patent Application Publication 2003-014860.)
However, a problem of there being noise in the element arises accompanying the driving of the Peltier element 92. Experimentation by the inventor has confirmed the superimposition of linear noise, as illustrated in FIG. 7, in particular. Because the location and timing with which the noise is superimposed is unspecified, there is a problem in that it is not possible to perform uniform corrections. The present inventors, through experimentation, have discovered that this problem occurs when there is variation in the driving voltage for the Peltier element 92 during the interval prior to the completion of the A/D conversion after the beginning of reading of the charge when the gate controlling means are open, and discovered that if the frequency of this fluctuation is high, then the noise becomes remarkable. The object of the present invention is to provide a high-quality image with low noise through controlling the noise in a radiographic device accompanying temperature control using a Peltier element.